A method of testing explosive and pyrotechnic devices involves exploding the devices inside swell sleeves. Swell sleeves have been used previously for measuring forces. In the present method, they are used to obtain quantitative indications of the energy released in explosions of the devices under test.

Figure 1. A Swell Sleeve is designed and fabricated to accept an explosive device. It is so named because its wall is thick enough not to burst yet thin enough to swell measurably when the device is exploded within it.

A swell sleeve is basically a thick-walled, hollow metal cylinder threaded at one end to accept a threaded surface on a device to be tested (see Figure 1). Once the device has been tightly threaded in place in the swell sleeve, the device-and-swell-sleeve assembly is placed in a test fixture, then the device is detonated.

Figure 2. These Diametral Swells as functions of axial position were obtained in swell-sleeve tests of explosive devices used to separate an external-tank assembly from a space shuttle.

After the explosion, the assembly is removed from the test fixture and placed in a coordinate-measuring machine for measurement of the diameter of the swell sleeve as a function of axial position. For each axial position, the original diameter of the sleeve is subtracted from the diameter of the sleeve as swollen by the explosion to obtain the diametral swelling as a function of axial position (see Figure 2). The amount of swelling is taken as a measure of the energy released in the explosion. The amount of swelling can be compared to a standard amount of swelling to determine whether the pyrotechnic device functioned as specified.

This work was done by Todd J. Hinkel, Richard J. Dean, Carl W. Hohmann, Scott C. Hacker, and Douglas W. Harrington of Johnson Space Center and James W. Bacak of Lockheed Engineering and Sciences Co. For further information, access the Technical Support Package (TSP) free on-line at www.techbriefs.com/tsp under the Mechanics category. MSC-23306.

NASA Tech Briefs Magazine

This article first appeared in the February, 2003 issue of NASA Tech Briefs Magazine.

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